Composite concrete slab and steel joist construction

ABSTRACT

A composite action open web steel joist and concrete slab interconnection is described. In one form of the invention, upper apex portions of the steel joist webbing protrude through the upper chord members of the joist, and through apertures provided in the sheet metal formwork placed over such joists prior to the pouring of the concrete slab, whereby said protruding apex portions will be encased within the slab to act as shear interconnection devices therein. Wedge members forced between such protruding joist apex portions and the sheet metal formwork serve to mechanically secure the joist and formwork together, to prevent leakage of the poured concrete through the sheet metal formwork openings, and to enhance the locking of the concrete slab to the protruding joist apex portions.

United States Patent 11 1 11 3,728,835 McManus [451 Apr. 24, 1973 COMPOSITE CONCRETE SLAB AND FOREIGN PATENTS OR APPLICATIONS STEEL JOIST CONSTRUCTION Inventor:

Filed:

Ira J. McManus, 39 Lincoln Avenue,

Florham Park, NJ. 07940 497,556 9/1954 Italy ..52/355 Primary ExaminerAlfred C. Perham Attorney-James J. Cannon [5 7 ABSTRACT A composite action open web steel joist and concrete slab interconnection is described. In one form of the 52 U.S.Cl .52/334, 52/336 Invention, upper apex portions of the steel 01st [51] ..E04b 1/16 t d th h th h d b 7 58 Field of Search ..52/334, 336, 355, we 9 3 mug e upper 6 of the 101st, and through apertures provided In the sheet metal formwork placed over such jOlStS prior to the pouring of the concrete slab, whereby said [56] References cued protruding apex portions will be encased within the UNITED STATES PATENTS slab to act as shear Interconnection devlces there n. Wedge members forced between such protruding joist 1,804,132 5/1931 Tashjian ..52/334 apex portions and the sheet metal formwork serve to 3,363,379 1/1968 Curran ..52/334 mechanically secure the joist and formwork together,

1,815,075 1931 Sersen ..5 /3 to prevent leakage of the poured concrete through the 3,094,813 6/1963 SaXe --5 sheet metal formwork openings, and to enhance the 2,180,317 11/193 Davis --5 locking of the concrete slab to the protruding joist Sealey X apex portions 2,096,921 10/1937 Sahlberg I ..52/334 2,558,946 7/1951 Fromson ..52/334 X 3 Claims, 11 Drawing Figures /5 1 '-.'-e." ws; --'o.- 1 'O 01:2 '0'. ',",O' r I. oi 2 if- Z :0. 0 :0 .'o... -o I. I I n: "I e I: 1 4 a 3 l 5 25 ,Z2 \20 /7 1- I I 544 r. \a

Patenfed April 24, 1973 AYAILZFLBLE 3,728,835

3 Sheets-Sheet INVENTOR. //-?/4 z/. M: MENUS Patented A ril 24, 1973 v3 Sheets-Sheet INVENTOR. #719 r], McMfi/Ul/S HTTOR/Vff).

COMPOSITE CONCRETE SLAB AND STEEL JOIST CONSTRUCTION This invention relates to concrete and steel construction, and is directed particularly to composite openweb steel joist and concrete slab construction to provide a more rigid and more economical composite floor or roof structure in building construction as compared with composite open-web joist-supported slabs heretofore devised.

A more particular object of the invention is to provide for composite action between a poured-in-place concrete slab and open-web steel joists utilizing apertured sheet metal formwork members in association with open-web steel joists, upper apex portions of the zig-zag webbing of which project through the upper joist chords so as to project through the formwork openings and act as shear members in the hardened concrete slab thereafter poured. These shear devices allow composite action between the concrete slab and the open-web steel joists, resulting in a stiffer and stronger floor or roof construction. The increase in composite strength thus achieved over ordinary construction permits the use of substantially lighter steel joist, thereby effecting a savings in construction costs.

Another object of the invention is to provide an improved composite open-web steel joist and concrete slab construction of the character above-described ineluding wedge means for interlocking protruding apex shear portions of the joist webbing with respect to the sheet metal formwork, thereby eliminating the need for welding such sheet metal formworkto the joist chords, as heretofore ordinarily done.

Yet another object of the invention is to provide a composite open-web steel joist and concrete slab construction wherein, instead of using upwardly-projecting apices of the joist web members as shear devices in the poured concrete slab, separate T or L-shaped bars or the like are welded with respect to top chord members of the joist so as to project through the apertures in the sheet metal framework members and be encased by the poured concrete slab.

Still another object of the invention is to provide a composite open web steel joist and concrete slab construction of the character above-described the mechanical design features of which are well adapted to manufacturing in the shop so as to minimize on the job assemblage procedures.

Still another object of the invention is to provide a composite steel and concrete construction of the above nature which is particularly well suited to use in conjunction with composite end connection between the joists and the supporting beams or girders of the building framework under construction so as to further enhance composite steel and concrete action in the support of live and dead loads in a finished building.

Other objects, features and advantages of the invention will be apparent from the following description when read with reference to the accompanying drawings. In the drawings, wherein like reference numerals denote corresponding parts throughout the several views:

FIG. 1 is a partial vertical cross-sectional view illustrating one form of composite concrete slab and steel joist construction embodying the invention;

FIG. 2 illustrates, on an enlarged scale, a concrete embedded upper end portion of the steel joist webbing showing a modification of the invention illustrated in FIG. 1 including use of a locking wedge for securing the joists to the slab supporting sheet metal formwork;

FIG. 3 is a top plan view of the interlocking device shown in FIG. 2, before pouring of the concrete slab;

FIG. 4 is a vertical cross-sectional view taken along the line 4-4 of FIG. 2 in the direction of the arrows;

FIG. 5 is a top plan view of a portion of the composite concrete slab and joist construction, before pouring of the slab, illustrating the apertures prepunched in the sheet metal formwork for the regular, through passage of upwardly-extending apex portions of the metal joist webbing;

FIG. 6 is a partial vertical cross-sectional view of a modified form of composite concrete slab and joist construction wherein a T-shape bars or headed studs are used as the embedded shear portions of the joists;

FIG. 7 is another modification of the invention wherein L-shaped bars are used as the embedded shear portions of the joists;

FIG. 8 is a partial vertical cross-sectional view of the invention as illustrated in FIG. 1, showing a modified form of apertured sheet metal formwork;

FIG. 9 is a top plan view of the form of the invention illustrated in FIG. 8, before the pouring of the concrete slab, illustrating how marginal rib positions of the formwork joist openings are bent down against the top chord of the joists to seal against the leakage of concrete;

FIG. 10 is a vertical cross-sectional view taken along the line 10-10 of FIG. 8 in the direction of the arrows; and

FIG. 11 is a vertical cross-sectional view of the corrugated sheet metal formwork showing how it is slit to provide for bending down against the top of the joist chord as illustrated FIGS. 9 and 10.

Referring now in detail to the drawings and considering first the embodiment of the invention illustrated in FIGS. 1 and 5, reference numeral 10 designates an open-web steel joist comprised of a pair of angle irons l1, 12 (only one illustrated in FIG. 1), welded opposedly along and a short distance below the apices at the upper side of a zig-zag, bent-rod web 13 to form the top chord of the joist, and a pair of angle iron members 14, 14 (only one shown in FIG. 1), welded opposedly along the apices at the other side, i.e., the bottom side, on the bent-rod web 13 to form the bottom chord of the joist. The joist 10 is thus formed along its length at regular intervals with web apex portions 15 projecting upwardly from the angle irons ll, 12, comprising the top chord. As shown in FIGS. 1 and 5, the steeljoists 10 are adapted, in floor or roof construction, to be supported at each end upon girders or beams 16, (only one illustrated in FIG. 1, by way of example). Preferably such end connections will be constructed according to the method and ineans described in my U.S. Pat. No. 3,392,499, issued July 16, 1968 and in my copending applications Ser. No. 751,930, filed Aug. 12, 1968 now U.S. Pat. No. 3,527,007, and Ser. No. 10,399 filed Feb. 11, 1970 now U.S. Pat. No. 3,624,980, also my copend- 7 ing application Ser. No. 79,022 filed Oct. 8, 1970, for

nection for steel joists such as are disclosed in my above-mentioned patent and patent applications.

The corrugated sheet metal formwork 17 placed upon the installed joists 10, (see FIG. is formed with the usual outwardly-extending ribs 18 for rigidity in supporting the concrete slab to be poured. However, instead of using ordinary corrugated sheet metal formwork uniformly corrugated throughout its area, the sheet metal formwork has corrugation ribs left out at regularly spaced intervals corresponding with the apexto-apex spacing of the bent-rod web portion 13 of the steel joists 10, to provide spaced, parallel, extra-wide trough portions 19 which are stamped in aligned rows along their lengths to provide substantially rectangular openings 20 so spaced and arranged for the projection therethrough of the upwardly projecting apex portions of the steel joists 10. After the concrete slab 21 is poured and hardens, there results a composite action between the poured-in-place concrete slab and the open-web steel joists 10, the upwardly projecting and embedded apex portions of the steel joist webbings serving as shear devices encased within the concrete. Composite action is thus effected between the slab and the open-web steel joists, resulting in a stiffer and stronger floor or roof construction. This composite structure also permits lighter weight steel construction of the open-web steel joists for more economical construction.

FIGS. 2, 3 and 4 illustrate a modification of the invention illustrated in FIGS. 1 and 5 and described above wherein bent sheet metal locking wedge devices 22 are utilized to supplement or entirely replace the usual procedure of welding the sheet metal formwork members 17 to the joists prior to the pouring of the concrete slab. Thus, as illustrated in FIGS. 2, 3 and 4, a locking wedge 22 comprising a bottom leg 23 and an angularly upwardly and inwardly-extending leg 24, having respective tapered edges 25 and 26, is force fitted, as by use of a hammer, in wedging position within and between the steel joist apex portions 15 and upper surface portions of the sheet metal formwork metal 17 to rigidly secure the joists and their associated sheet metal formwork sheets together. Another advantage in the use of the locking wedge devices 22 resides in the fact that they serve to enclose the space between the top chord angle irons ll, 12 or the open-web steel joists immediately below the upwardly-projecting apex portions 15 to minimize the possibility of concrete leakage therethrough upon pouring of the concrete slab. Still another advantage resulting with the use of the sheet metal locking wedges 22 is the enhanced keying action between the concrete slab and the joists because of the additional concrete surrounding the devices.

FIG. 6 illustrated a modification of the invention illustrated in FIGS. 1 and 5 utilizing standard open-web joists 10a comprising a zig-zag bend-rod web 13a having opposed top chord angle iron members affixed at each side along the apices of said bent rod member. In this embodiment of the invention upwardly extending T-bar or headed stud members 27 are welded between the upper chord angle iron members 11, 11a, (only one illustrated in FIG. 6), in the vicinity of the webbing apices. The T-bar members 27 are utilized as shear devices effecting composite action as described above.

FIG. 7 illustrates a variation of the embodiment illustrated in FIG. 6 wherein an inverted L-bar member 28 is utilized as the embedded shear device instead of the T-bar member 27 as shown in FIG. 6. As in the construction illustrated in FIGS. 2, 3 and 4 wherein locking wedges 22 are utilized to mechanically secure the joists to the corrugated sheet metal formwork, it will be understood that locking wedge devices could readily be devised for supplemental use in the embodiments of the invention illustrated in FIGS. 6 and 7.

FIGS. 8 through 11 illustrate still another modification of the invention shown in FIGS. 1 and 5 wherein, in the sheet metal formwork member 17, trough portions 19 are omitted and metal formwork sheets uniformly corrugated throughout their entire width are utilized, the regularly-spaced openings 20 being stamped or otherwise cut, preferably in the shop, to pass cross-wise and symmetrically with respect to appropriately spaced corrugation ribs 18, such apertured ribs being designated by reference numeral 30. As illustrated by the broken-line representation thereof in FIG. 9, central marginal side well portions of the apertured ribs 30 are perpendicularly outwardly slit to provide for hammering or otherwise bending down opposed metal flap portions 32, 33 at each side of the opening 20. After assemblage of the sheet metal formwork members 17 upon the supporting joists 11, the metal flap portions 32, 33 will be hammered or otherwise bent down into abutting engagement with top portions of the top chord angle iron members 11 and 12 of the joists, as illustrated in FIG. 10. The high portions of the apertured corrugation ribs 30 are thus closed off to minimize the possibility of leakage of concrete upon subsequent pouring of the concrete slab 21. An advantage of the embodiment of the invention illustrated in FIGS. 8 through 11 over that illustrated in FIGS. 1 and 5 resided in the extra strength in the form work afforded by the retaining of the sheet metal framework corrugation ribs 30. As shown in the embodiment of the invention illustrated in FIGS. 2 through 5, it is, of course, to be under stood that locking wedge devices could also be used to mechanically secure the joist webbing apex shear portions 15 with respect to the sheet metal formwork.

While I have illustrated and described herein several forms in which my invention can conveniently be embodied in practice, it is to be understood that these forms are presented by way of example only and not in a limiting sense. The invention, in brief, includes all the modifications and embodiments coming within the scope and spirit of the following claims.

What I claim as new and desire to secure by Letters Patent is:

1. In a composite open-web steel joist and concrete rality of apertures therein for the through passage of said upwardlyiextending shear members, wedge means for rigidly securing said apex portions with respect to said corrugated metalformwork member including a cooperating bottom leg portion to close apertures in said metal formwork member to prevent the escape of poured concrete therefrom, and a poured-in-place concrete slab upon said formwork member and encasing said upwardly-extending shear members, means wherein said top chord is displaced somewhat downwardly of the upper ends of said apex portions and rigidly secured to said webbing member constituting said apex portions as shear members in said composite steel joist and concrete slab construction, said wedge means comprising an angularly bent piece of sheet metal including an upwardly extending leg having tapered edge portions supported by said bottom leg portion defining a substantially triangular shaped crosssection wedge means.

2. A composite open-web steel joist and concrete slab construction as defined in claim 1; wherein said corrugated sheet metal formwork member is formed with. regularly-spaced, parallel troughs including said bottom portions, said apertures being arranged in said bottom portions.

3. A composite open-web steel joist and concrete slab construction as defined in claim 1 wherein said formwork member includes apertures of rectangular shape having side flap portions and pass transversely of longitudinal ribs of said corrugated formwork member, said flap portions of said apertures being bent down into abutting engagement with top portions of the top angle iron members of the joist members, and installation of said wedge means between said upper apexes of said webbing member and said metal formwork members before said concrete slab is poured-in-place. 

1. In a composite open-web steel joist and concrete slab construction, the combination comprising, an open-web joist member having a zig-zag bent metal webbing member and top and bottom chords, said zig-zag webbing member having a substantially uniformly spaced series of upper extending apex portions with respect to and along which said top chord is affixed, a plurality of shear members extending upwardly of said top chord at said portions, a heavy corrugated solid sheet-like metal formwork member having substantially flat bottom and top portions received in seating engagement upon said joist top chord and having a plurality of apertures therein for the through passage of said upwardly-extending shear members, wedge means for rigidly securing said apex portions with respect to said corrugated metal formwork member including a cooperating bottom leg portion to close apertures in said metal formwork member to prevent the escape of poured concrete therefrom, and a poured-in-place concrete slab upon said formwork member and encasing said upwardly-extending shear members, means wherein said top chord is displaced somewhat downwardly of the upper ends of said apex portions and rigidly secured to said webbing member constituting said apex portions as shear members in said composite steel joist and concrete slab construction, said wedge means comprising an angularly bent piece of sheet metal including an upwardly extending leg having tapered edge portions supported by said bottom leg portion defining a substantially triangular shaped cross-section wedge means.
 2. A composite open-web steel joist and concrete slab construction as defined in claim 1; wherein said corrugated shEet metal formwork member is formed with regularly-spaced, parallel troughs including said bottom portions, said apertures being arranged in said bottom portions.
 3. A composite open-web steel joist and concrete slab construction as defined in claim 1 wherein said formwork member includes apertures of rectangular shape having side flap portions and pass transversely of longitudinal ribs of said corrugated formwork member, said flap portions of said apertures being bent down into abutting engagement with top portions of the top angle iron members of the joist members, and installation of said wedge means between said upper apexes of said webbing member and said metal formwork members before said concrete slab is poured-in-place. 